This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Pax7 is a muscle transcription factor necessary for satellite cell function in skeletal muscle regeneration. The levels of Pax7 protein are regulated post-transcriptionally and affect the decision of a satellite cell to self-renew or commit to myogenic differentiation. Part of this decision appears to be determined by the levels of MyoD and myogenin in satellite cells. High Pax7 levels induce MyoD degradation and high MyoD levels cause Pax7 degradation. We hypothesize that these proteins compete for a common factor that is required for DNA binding and stabilization. The goal of this collaboration is to identify proteins in proliferating skeletal muscle cells that interact directly or indirectly with Pax7.